Int 68 Fn FB  - Appc/pc - Convert                                          [N]

   AH = FBh
   DS:DX -> control block (see #3378)

Return: control block updated

Format of APPC/PC "CONVERT" control block:
Offset Size    Description (Table 3378)
 00h 12 BYTEs  reserved
 0Ch   WORD    1A00h (verb "CONVERT")
 0Eh  6 BYTEs  00h
 14h   DWORD   (big-endian) return code
 18h   BYTE    conversion
       00h ASCII to EBCDIC
       01h EBCDIC to ASCII
 19h   BYTE    character set
       00h AE
       01h A
       02h G
 1Ah   WORD    length of string to convert
 1Ch   DWORD   pointer to source
 20h   DWORD   pointer to target